Abstract

A scheme is proposed for detecting a concealed source of ionizing radiation by observing the occurrence of breakdown in atmospheric air by an electromagnetic wave whose electric field surpasses the breakdown field in a limited volume. The volume is chosen to be smaller than the reciprocal of the naturally occurring concentration of free electrons. The pulse duration of the electromagnetic wave must exceed the avalanchebreakdown time (10–200 ns) and could profitably be as long as the statistical lag time in ambient air (typically, microseconds). Candidate pulsed electromagnetic sources over a wavelength range, , are evaluated. Suitable candidate sources are found to be a 670 GHz gyrotron oscillator with 200 kW, output pulses and a Transversely Excited Atmospheric-Pressure (TEA) laser with 30 MW, 100 ns output pulses. A system based on 670 GHz gyrotron would have superior sensitivity. A system based on the TEA laser could have a longer range .

Received 10 June 2010Accepted 30 July 2010Published online 24 September 2010

Acknowledgments:

This study has been supported by the Office of Naval Research under Grant Nos. N000140910596 and N000140911190. Valuable discussions were held in the course of this work with Thomas Antonsen, Jr., Gennady Milikh, Quentin Saulter, Ali Mohamed, Joseph Silverman, Mohamad Al-Sheikhly, and Amit Kesar.